The invention relates to a method for the bending of workpieces by swivel bending jaws, the bent-off part assuming a predetermined bending angle with respect to the workpiece, as well as an apparatus for this.
In many areas of application, it is necessary to bend off a certain region at a certain angle from a previously worked or unworked workpiece. A known conventional bending method works with a bending punch and a platen, between which the workpiece is held. Bending punch and platen then move together with the workpiece past a bending jaw, the projecting part of the workpiece being bent off by the bending radius of the bending punch.
A particularly disadvantageous aspect of this bending method is that a workpiece is bent off into a fixed gap. Furthermore, when the workpiece meets the bending jaw, a zone occurs on the workpiece in which material is displaced. Furthermore, the bending gap must be precisely determined in order for a correct bending to be performed. Workpiece thickness tolerances cannot be taken into account. A possible springback of the bent-off part after release from the bending punch and platen cannot be counteracted.
In many areas of application, however, an absolutely precise bending angle is just what is required. Therefore, to compensate for the springback, the so-called Rotax method has been developed. A description of this method is to be found in European Patent Application 0,155,228. The workpiece to be bent is placed onto two spaced apart jaws, which can turn about their longitudinal axis. In the space between the two jaws, a bending punch acts on the workpiece, so that the latter is bent off with simultaneous turning of the rotary jaws about their longitudinal axis without their own drive. After reaching a predetermined bending angle, the bending punch is raised again and the angle at which the surfaces of the two bending jaws are to each other is measured. This angle is then used to conclude the actual set angle. If this does not coincide with the set bending angle, the bending punch is lowered once again and the workpiece is correspondingly bent over. However, no absolutely accurate measurement of the bending angle actually achieved is possible by this indirect measurement. If, for example, the surfaces of the bending jaws have remainders of dirt adhering to them, these falsify the result from which the actual bending angle is concluded.
Furthermore, likewise only a bending in one operation is possible by this method.
Furthermore, it must be taken into account when bending a material that materials of the widest variety of strengths, material microstructures and cross-sections have to be worked. Depending on these parameters, the springback under bending is also different to a certain extent. Both material thickness tolerances and strength variations change the bending angle by different springback and parts which are not dimensionally true result.
The inventor has set himself the object of developing a method and apparatus of the abovementioned type by means of which bending angles can be produced independently of the strength, the material microstructure or the thickness of the workpiece in closest tolerance ranges, several bendings being performed simultaneously in one operation on one workpiece.